Tree-devastating beetle found in Gaithersburg

Montgomery is seventh Maryland county to host emerald ash borer

Maryland Department of Agriculture
The emerald ash borer was recently found in Gaithersburg. This tiny Asian beetle is credited with destroying thousands of trees across Maryland.

A destructive invasive beetle was discovered in Gaithersburg last week, signaling the pest’s first presence in Montgomery County and a threat to local ash trees.

The Maryland Department of Agriculture announced June 29 that workers discovered the presence of the emerald ash borer beetle — or EAB — in a tree near Gaithersburg, said Jim Arnoult, director of the city’s Public Works department. The Asian beetle is an invasive insect that feeds on and eventually kills ash trees, according to the department.

There are more than 7 million ash trees in Maryland, which is a landscaping tree, according to the department. State agriculture officials say the beetle poses a threat to Maryland’s agricultural industry and has the potential to devastate its ash population.

Adam Newhart, a certified arborist for the City of Gaithersburg, said while there are no precise counts, there are more than 1,000 ash trees in the city, mostly in city parks. There are fewer than 500 city-maintained trees in rights of way in Gaithersburg.

To try and stem the spread of the beetle, Newhart said the city will begin treating the soil around ash trees with the pesticide Imidacloprid, according to the National Pesticide Information Center.

Newhart said pre-treating the trees is the only known method for preventing their destruction besides tearing them down and replacing them. The city will repeat the process every other year.

“If you don’t treat the trees, over time EAB gets inside and kill them,” he said. “They’ll fall after just a few years.”

Newhart said the city has no estimates for the cost of treating the trees.

Once in a tree, the ash borer will kill it after roughly one year, according to the Maryland Department of Agriculture.

The greenhouse and nursery industry, essentially fueled partly by trees, was the second largest agricultural sector in Maryland in 2010, accounting for $1.96 billion in gross receipts, according to National Agricultural Statistic Service. In a June 29 release, state Agriculture Secretary Buddy Hance called the ash “one of the most important urban trees in Maryland.”

The borer has been reported in 14 states and is credited with destroying more than 10 million trees nationwide.

The ash borer has been found in seven Maryland counties, first discovered in Prince George’s County in 2003 in an ash nursery.

Last year, Hance ordered a quarantine for all 14 counties west of the Chesapeake Bay in hopes of stopping its spread to the Eastern Shore. In May, he announced the release of the first of 16,000 egg parasitoid; an Asian wasp that is reportedly stingless which kills the ash borer by laying its eggs in ash borer eggs.

Robert Manwell, a spokesman of the Wisconsin Department of Natural Resources, one of 13 states also infected with the ash borer, said his state has been utilizing quarantines — which prohibit the movement of firewood from areas where the ash borer is known to exist. He said the wasps have only proven effective in areas where the borer is widespread and the most effective method is for a state to reduce its reliance on the ash tree.

“The best method we know is having a diverse stock [of trees],” he said.

The ash tree became more prominent as an urban tree after the population of Dutch elms dropped following the spread of Dutch elm disease more than 20 years ago, Manwell said.